1. Go to the Administration Block and click on Gradebook Setup.
2. In the next screen, look again in the left-hand block area and click on Letters.
3. This shows how the current letter grades are defined. To change the grade ranges, click the red words Edit Grade Letters at the top of the page.
4. In order to make any changes, click on the checkbox for Override Site Defaults.
5. Then enter then minimum grade required for each letter grade in the blank next to that letter. (Moodle will accept 2 decimal places for rounding purposes if desired)
6. Delete any Grade Letters that you do not want to use, while making sure that letters are in consecutive blanks. Avoid leaving a blank Grade Letter between two filled-in Grade Letter fields, as in the following image:
7. When done, click the blue Save Changes button. The changes will affect the current gradebook for the course (if letters are visible to students).